1. Technical Field
The present invention relates to a micro electro mechanical systems (MEMS) sensor module package and a method of manufacturing the same.
2. Description of the Related Art
Micro electro mechanical systems (MEMS), also known as micro machines or micro systems technology, is the technology of manufacturing very small devices in μm or mm size based on semiconductor processing technologies. By processing silicon, crystal, glass or the like, micro mechanical structures may be manufactured such as very large scale integrated circuits (VLSI), micro gears having a thickness half that of a strand of hair, and fingernail-sized hard disks, sensors and actuators. It has a sophisticated three-dimensional structure in which surface micromachining is processed in bulk silicon etching method through evaporation, etching and the like.
A MEMS sensor manufactured by using such MEMS has been used in various applications, for example, a military application such as an artificial satellite, a missile, an unmanned aircraft, a vehicle application such as an air bag for a vehicle, electronic stability control (ESC), a black box for a vehicle, a shaking prevention application of a camcorder, a motion sensing application of a mobile phone or a game console, or the like.
A MEMS sensor is configured with a mass body adhered to an elastic substrate such as a membrane to measure acceleration, angular velocity, force, pressure or the like. That is, with the configuration, a MEMS sensor calculates acceleration by measuring inertial force applied to the mass body, calculates angular velocity by measuring Coriolis force applied to the mass body, and calculates force by measuring external force directly applied to the mass body.
Specifically, acceleration and angular velocity are measured using a MEMS sensor as follows.
First, acceleration may be calculated using Newton's law of motion “F=ma,” where “F” represents inertial force applied to the mass body, “m” represents the mass of the mass body, and “a” is acceleration to be measured. Among others, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the sensed inertial force F by the mass m of the mass body which is a constant.
Further, the angular velocity may be obtained using Coriolis force “F=2 mΩ×v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity v of the mass body and the mass m of the mass body are already known, the angular velocity Ω may be obtained by sensing the Coriolis force (F) applied to the mass body.
Such a MEMS sensor is packaged in a such manner that an application specific integrated circuit (ASIC) is attached on a sensor element using an epoxy or the like, and then each of the elements is electrically connected to a printed circuit board (PCB) by wire bonding.
In such a MEMS sensor module package, since an acceleration sensor and a gyro sensor are separate devices and an ASIC is also separately provided, there are many I/O counts. Therefore, it is very difficult to make the package light, thin and simple with those additional devices.
In this connection, Patent Document 1 teaches that a MEMS chip and an ASIC chip are stacked on a wafer, in which a cap is attached on the MEMS chip and the ASIC chip is attached on the cap, and the ASIC ship and the MEMS chip are electrically connected by wire and molded with a compound resin. Then, the compound resin is selectively removed to form holes for attaching input/output terminals, by which solder balls are soldered onto the ASIC chip.
In conventional MEMS sensor module packages including that disclosed in Patent Document 1, however, as mentioned earlier, since a MEMS chip and an ASIC chip are stacked on a wafer, wafer bonding tools and schemes need to be used in order to manufacture it, but it is difficult to process in a general process. Further, it is also a problem in that yield rate of ASIC chips and MEMS chips may deteriorate during the attaching process.
In addition, wire bonding is made on four surfaces of the ASIC chips and the MEMS chips, and thus the size of a MEMS sensor module package is increased. Further, since the stack structure has a pyramid shape, the space of the PCB is not efficiently utilized and thus additional space may be needed as the number of stacks is increased.